Type:

commitOnSelChange :boolean

(PDF 1.5) If set, the new value shall be committed as soon as a selection is made (commonly with the pointing device). In this case, supplying a value for a field involves three actions: selecting the field for fill-in, selecting a choice for the fill-in value, and leaving that field, which finalizes or “commits” the data choice and triggers any actions associated with the entry or changing of this data. If this flag is on, then processing does not wait for leaving the field action to occur, but immediately proceeds to the third step.
This option enables applications to perform an action once a selection is made, without requiring the user to exit the field. If clear, the new value is not committed until the user exits the field.

Type:

readOnly :boolean

If set, the user may not change the value of the field. Any associated widget annotations will not interact with the user; that is, they will not respond to mouse clicks or change their appearance in response to mouse motions. This flag is useful for fields whose values are computed or imported from a database.

Type:

showWhenPrinted :boolean

(PDF 1.2) If set, print the annotation when the page is printed. If clear, never print the annotation, regardless of wether is is displayed on the screen.
NOTE 2 This can be useful for annotations representing interactive pushbuttons, which would serve no meaningful purpose on the printed page.

Type:

boolean

sort :boolean

If set, the field’s option items shall be sorted alphabetically. This flag is intended for use by writers, not by readers. Conforming readers shall display the options in the order in which they occur in the Opt array (see Table 231).